Neutrophil function tests in Chinese newborn infants

by Wan, Shek-kong

(Uncorrected OCR) ABSTRACT OF THESIS ENTITLED 'NEUTROPHIL FUNCTION TESTS IN CHINESE NEWBORN INFANTS'

SUBMITTED BY THOMAS SHEK-KONG WAN

FOR THE DEGREE OF MASTER OF PHILOSOPHY

AT THE UNIVERSITY OF HONG KONG IN SEPTEMBER, 1991.

In most clinical immunology laboratories, a large quantity of blood is required to measure the neutrophil function profile, which includes complete blood cell count, neutrophil phagocytic activity, neutrophil chemotaxis and nitroblue tetrazolium reduction capacity. Hence, it is difficult to perform the neutrophil function tests on small infants. This is a study to standardize a micro-technique method which can be used in paediatric patients.

With an aim to do neutrophil function tests in infants, we had tried to improve the isolation of neutrophil technique, in which to increase the neutrophil yield after separation procedures. We confirmed that a higher yield of neutrophils could be obtained by using Hypaque-Ficoll centrifugation than using dextran sedimentation. The neutrophil function profile (candidacidal assay, chemotactic assay, phagocytic assay and nitroblue tetrazolium reduction test) of newborns could be performed on two milliliter of heparinized blood and 0.25 ml EDTA blood. Our standard methods for the measurement of neutrophil phagocytosis and

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candidacidal abilities were modified from the conventional method described by Lehrer and Cline (1969; see also Lehrer, 1970). Chemotaxis under agarose gel method was done according to the method described by Nelson and associates (1975). Various conditions had been verified and standardized in our studies. We conducted a study to standardize the micro-nitroblue tetrazolium reduction test procedures and to clarify the effects of anticoagulants and incubation time on neutrophil nitroblue tetrazolium reduction score. We can conclude that when performing the NBT tests, the blood samples should best be anticoagulated with EDTA to ensure more consistent results.

Micro-methods of neutrophil function tests were tested for their reproducibility by using adult blood. Their coefficient of variation were within desirable limits for biological test system. The reference range of neutrophil functions for 21 voluntary healthy adults was established. Neutrophil functions of Chinese newborn infants were also performed by using these standard micro-methods. The reference ranges (mean + S.D.) of candidacidal activity, phagocytic activity and phagocytic index were 18.00% ?7.17%, 62.48% + 12.10% and 1.55 + 0.55, respectively. The reference ranges (mean ?S.D.) of chemotactic migration distance (A), spontaneous migration distance (B), chemotactic index (A/B), chemotactic differential (A-B) and chemotactic differential ?+B)-(C+O?were 0.92 mm ?0.32

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mm, 0.42 mm + 0.15 mm, 2.37 ?0.67, 0.50 mm ?0.22 mm and 0.45 mm ?0.23 mm, respectively. The reference ranges (mean ?S.D.) of spontaneous nitroblue tetrazolium reduction score and E. coli endotoxin stimulated nitroblue tetrazolium

reduction score were 27.38% ?18.02% and 61.77% + 19.72%,

respectively.

When comparing to adult neutrophils, candidacidal

activity and chemotactic values of neonate neutrophils were

lower.

Phagocytosis ability of neonates was not

significantly different from those of normal adults.

However, nitroblue tetrazolium reduction capacity of

neonates was significantly higher than that of normal adults. Candidacidal activity was significantly depressed in male infants comparing with that of female babies.

Phagocytosis ability and nitroblue tetrazolium reduction

capacity of male neonates and female neonates were

compatible with each other. Neutrophil functions showed no difference in the infants of various post-natal ages tested. Candidacidal activity, phagocytosis ability and nitroblue tetrazolium reduction capacity had no significant difference

between normal birth weight babies and low birth weight babies. Chemotactic differentials ?-B) and (A+B)-(C+D?

were significantly diminished in low birth weight babies comparing with normal birth weight babies. In addition, candidacidal activity, phagocytosis ability and nitroblue

tetrazolium reduction capacity had no significant difference

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between premature babies and full-term babies. Chemotactic migration (A), chemotactic index (A/B) and chemotactic differentials ?-B) and (A+B)-(C+O) of premature babies were significantly lower than that of full-term babies. Candidacidal activity had no significant difference among glucose-6-phosphate dehydrogenase deficient babies, and both male and female babies with normal glucose-6-phosphate dehydrogenase activity. But, phagocytosis ability was significantly depressed in neonates with glucose-6-phosphate dehydrogenase deficiency.

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